Conventionally, an exhaust heat recovery device is known, for example, in JP 2008-190437A. The exhaust heat recovery device includes a heat recovery unit and a coolant flow adjusting unit. The heat recovery unit is located in an exhaust gas pipe of an internal combustion engine to perform heat exchange between coolant flowing therein and exhaust gas passing through the exhaust gas pipe. A catalyst is provided in the exhaust heat recovery device such that heating of the catalyst is performed by using exhaust gas in the exhaust gas pipe. The coolant flow adjusting unit is located to adjust a flow amount of the coolant flowing in the heat recovery unit. When the heating of the catalyst is performed after the operation of the engine starts, the flow amount of the coolant flowing through the heat recovery unit is reduced to be lower than a predetermined amount by the coolant flow adjusting unit, thereby reducing a heat-absorbing amount of the coolant from the reaction heat generated by the catalyst.
However, in the exhaust heat recovery device described in JP 2008-190437A, because the coolant and the exhaust gas are directly heat-exchanged in the heat recovery unit, the reaction heat generated from the catalyst may be easily transmitted to the coolant. During the heating of the catalyst after the engine starts operating, when the flow amount of the coolant is made lower than the predetermined amount in order to facilitate the heating of the catalyst, the coolant may be boiled by receiving heat from the exhaust gas. Conversely, if the flow amount is adjusted by the coolant flow adjusting unit to a value without causing the boiling of the coolant, the heating of the catalyst may delay. Thus, it may be difficult to facilitate the heating of the catalyst while preventing the boiling of the coolant, in the above exhaust heat recovery device.